Kinetics of the reactions of ethynyl radical with acetylene, hydrogen, and deuterium

Abstract

5875580 nm. Because the 9-10-nm bandpass of the 580-nm interference filter is not negligible in comparison with the width of the 580-nm absorption band, this is an "effective" value of eh,-. By use of a value of 5 X lo4 M-' cm-1 for C~. -,~O a value of 0.18 is obtained for Gk.-. This can be compared with G(free ions) in cyclohexane ~0 . 1 5 . 2~ A value of Gh.greater than G(free ions) is expected because on a time scale of a few hundred nanoseconds the contribution of C02'-(geminate) + Pe -Pee-(geminate) + C02 should be significant. Combmed with the uncertainty in h-, this preclude using the value of GPc.derived here as an accurate measure of G(free ions). COrtC~USiOM

A modified potential energy surface for the C2H+H2↔C2H2+H reaction and a theoretical study on its rate constants

“…The effective barrier of the MWB PES is 2.29 kcal/mol, which falls within the values of 2.0-2.5 kcal/mol suggested by many groups [5,7,13,[19][20][21]. The results of the reaction heat (À28.16 and À30.11 kcal/mol in the MWB PES and the ab initio cases, respectively) are in good agreement with the experimental value (À28.72 kcal/mol) [33] within experimental errors.…”

“…Table 4 presents the CVT/SCT rate constants for the C 2 H + H 2 ! C 2 H 2 + H reaction, along with the available experimental results [4][5][6][7][8][9][10][11][12][13][14][15][16], for the temperature range 20-4650 K. In Fig. 3, the rate constants of the present work are compared with the experimental data [4][5][6][7][8][9][10][11][12][13][14][15][16] and the quantum dynamics results calculated recently by Wang [26] basing on the WB PES.…”

“…The linear transition state was located and the barrier height was found to be 4.0 kcal/mol. According to the recent conclusions [5,7,13,[19][20][21], lower barrier heights of 2.0-2.5 kcal/mol may reproduce the experimental rate constants better over a broad range of temperatures. Based on the properties of the saddle point reported by Harding et al [18], Wang and Bowman [23] have constructed the first global PES of the C 2 H + H 2 system and accomplished a quantum dynamics calculation.…”

“…The C 2 H + H 2 M C 2 H 2 + H reaction has been extensively studied in the past few decades. Experimentally, the rate constants have been measured with various methods over wide temperature range of 178-4650 K [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Theoretically, the ab initio calculations have been carried out by a few groups [18][19][20][21][22].…”

“…Second, on the basis of the stationary point properties of the ab initio data as well as the experimental results, the barrier height of the WB PES is reduced to a reasonable value, and then the MWB PES will be obtained. And finally, the rate constants based on the MWB PES and the ab initio data in the present work will be calculated and compared with the experimental results [4][5][6][7][8][9][10][11][12][13][14][15][16].…”